 
  
  
                | Trade mark | Added impurity | Impurity quantity % | Other impurity | Electric discharged power | Color sign | 
| WL10 | La203 | 0.8~1.2 | <0.2% | 2.6~2.7 | black | 
| WL15 | La203 | 1.3~1.7 | <0.2% | 2.8~3.0 | gold | 
| WL20 | La203 | 1.8~2.2 | <0.2% | 2.8~3.2 | Sky blue |